//-------------------------------------------------------------------
//	flagvals.cpp
//
//	This program displays a graphical visualization for values
//	of the processor's status flags (using gcc inline assembly 
//	language to obtain access to the Pentium EFLAGS register).
//
//	programmer: ALLAN CRUSE
//	written on: 06 NOV 2003
//	revised on: 10 NOV 2003
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), write(), close() 
#include <termios.h>	// for tcgetattr(), tcsetattr() 
#include <sys/mman.h>	// for mmap() 
#include <sys/io.h>	// for iopl() 

#define VRAM_BASE_ADDRESS 0xA0000000 
#define VGA_MEMORY_LENGTH ( 4 << 20) 

unsigned char *vram = (unsigned char*)VRAM_BASE_ADDRESS; 
const int display_mode = 0x4103, hres = 800, vres = 600; 

unsigned char *c = &vram[  28*hres + 7 ];
unsigned char *p = &vram[  28*hres + 256 + 15 ];
unsigned char *a = &vram[  28*hres + 512 + 23 ];
unsigned char *z = &vram[ 314*hres + 7 ];
unsigned char *s = &vram[ 314*hres + 256 + 15 ];
unsigned char *o = &vram[ 314*hres + 512 + 23 ];

void draw_rectangle( int x, int y, int h, int v, int color ) 
{
	int	minx = x, miny = y, maxx = x+h-1, maxy = y+v-1; 

	do { vram[ y*hres + x ] = color; ++x; } while ( x < maxx ); 
	do { vram[ y*hres + x ] = color; ++y; } while ( y < maxy ); 
	do { vram[ y*hres + x ] = color; --x; } while ( x > minx ); 
	do { vram[ y*hres + x ] = color; --y; } while ( y > miny ); 
}

int map_system_memory( int base, int size ) 
{
	int	fd = open( "/dev/vram", O_RDWR ); 
	if ( fd < 0 ) { perror( "/dev/vram" ); return -1; } 
	int	prot = PROT_READ | PROT_WRITE; 
	int	flag = MAP_FIXED | MAP_SHARED; 
	void	*mm = (void*)base; 
	if ( mmap( mm, size, prot, flag, fd, 0 ) == MAP_FAILED ) 
		{ perror( "mmap" ); return -1; } 
	close( fd ); 
}


int main( int argc, char **argv )
{
	if ( iopl( 3 ) ) { perror( "iopl" ); exit(1); }
	system( "/sbin/insmod vram.o" ); 
	map_system_memory( VRAM_BASE_ADDRESS, VGA_MEMORY_LENGTH ); 

	struct termios	otty; 
	tcgetattr( 0, &otty ); 
	struct termios	tty = otty; 
	tty.c_lflag &= ~( ICANON | ECHO | ISIG ); 
	tty.c_cc[ VMIN ] = 1; 
	tty.c_cc[ VTIME ] = 0; 
	tcsetattr( 0, TCSAFLUSH, &tty ); 

	char	command[ 40 ]; 
	sprintf( command, " clear ; mode3 %d ", display_mode ); 
	system( command ); 

	int	color = 15; 
	draw_rectangle( 0, 0, hres, vres, color ); 
	getchar(); 

	short	flags[ 256 ][ 256 ];
	for (int i = 0; i < 256; i++)
		for (int j = 0; j < 256; j++)
			{
			int	status;
			asm(" movl %0, %%eax " : : "m" (i) );
			asm(" movl %0, %%edx " : : "m" (j) );
			asm(" addb %al, %dl " );
			// asm(" subb %al, %dl " );
			// asm(" xorb %al, %dl " );
			// asm(" mulb %dl " );
			asm(" pushfl ; popl %eax ");
			asm(" movl %%eax, %0 " : "=m" (status) );
			flags[ i ][ j ] = status;
			}
	
	for (int i = 0; i < 256; i++)
		for (int j = 0; j < 256; j++)
			{
			int	k = i*hres + j;
			c[ k ] = ( flags[ i ][ j ] & (1<<0) ) ? 4 : 2;	
			p[ k ] = ( flags[ i ][ j ] & (1<<2) ) ? 4 : 2;	
			a[ k ] = ( flags[ i ][ j ] & (1<<4) ) ? 4 : 2;	
			z[ k ] = ( flags[ i ][ j ] & (1<<6) ) ? 4 : 2;	
			s[ k ] = ( flags[ i ][ j ] & (1<<7) ) ? 4 : 2;	
			o[ k ] = ( flags[ i ][ j ] & (1<<11) ) ? 4 : 2;	
			}
	getchar();
	
	system( " mode3 3 " ); 
	tcsetattr( 0, TCSAFLUSH, &otty ); 
}